A few things from a conversation with a friend that has been dealing with this:
Got the truck back from the dealer last night with new leaf springs, new catalytic converter, and new passenger side cam phaser and cam.
Unfortunately, the engine still makes the dreaded knocking/ rattle on. Turns out the driver's side cam needs replacing as well. If you're having any cam phaser issues then get to the dealer because Ford just released the revised parts. Supposedly this is the cure-all for the cam phaser issue that's existed in EcoBoost engines since 2013.
When I asked about what problems other than noise could/did arise:
There were many moments of a decrease in power and a few times the truck wouldn’t start. I spoke to a few techs about it and there seems to be a 50/50 split. Some say it’s just noise and not an issue. Others say it’s a major issue. The tech who replaced mine said the last one he worked on had completely broken the cam gear off.
From what I've seen of the 8 or so cases thus far, the noise may or may not be fixed by the repair, and seems to be a split on whether or not it causes major issues or not. As the techs noted, half the time it is just noise, half the time it causes other problems.
I'd also note that the 10 speed makes a lot of noise for the first few seconds during startup, and that seems to be normal. So a rattling that is similar to bad phasers/timing chain IS normal for our trucks (being the 10 speed) but the actual noise (which is close, but louder and shorter in duration) is NOT normal. Makes it hard to tell, especially since both noises seem to be irregular when they occur.
Personally, I'm loathe for my engine to be torn into for just a noise. But it would also suck to have the chain go kaput outside of warranty.